Programmers and computer scientists call the action of coercing a floating-point or double to an integer **truncation**. The verb is **to truncate**.

> trunc
>
> Truncate value
>
> Rounds x toward zero, returning the nearest integral value that is not larger in magnitude than x.
>
> [C++ reference][1]

Perhaps your C++ function could be a Boolean called *isTruncated*.

  [1]: http://www.cplusplus.com/reference/cmath/trunc/